Veneer-sheet-feeding apparatus

ABSTRACT

In plywood layup apparatus, veneer sheets are fed from a vertical stack onto a horizontal conveyor by a movable vacuum head that grips the uppermost veneer sheet in the stack and shifts it towards the conveyor. A pair of pinch rollers are positioned between the vacuum head and conveyor to separate a veneer sheet from the vacuum head by gripping and driving the veneer sheet forward onto the conveyor. Sometimes two veneer sheets, one superposed upon another, are fed between the pinch rollers by the vacuum head. This condition is detected automatically by sensing means which activate controls for lifting the upper pinch roller and holding the vacuum head in a sheet-feeding position. Friction force of the lower pinch roller acts on the lower veneer sheet only. The lower veneer sheet is driven forward onto the conveyor but the upper veneer sheet is held stationary by the vacuum head. After the lower veneer sheet has been separated and spaced from the upper veneer sheet, the upper pinch roller is lowered, forcing the upper veneer sheet into driving contact with the lower pinch roller. Thus, the upper veneer sheet is separated from the vacuum head and driven forward onto the conveyor.

United Statesv Patent [72] Inventors Ronald J. Billett Sunnyvale;

Terence R. West, San Jose, both of, Calif. [21 Appl. No. 887,876

[22] Filed Dec. 24, I969 [45] Patented Aug. 17, 1971 [73] Assignee FMC Corporation San Jose, Calif.

[54] VENEER-SHEET-FEEDING APPARATUS 6 Claims, 20 Drawing Figs.

52 U.S.Cl. 271/14,

' 214/35 D, 271/26, 271/47, 271/57 51] Int.Cl B65h5/l0 so FieldofSearch ..271/10,11,

Primary Examiner-Joseph Wegbreit Assistant ExaminerBruce l-l. Stoner, Jr. Attorneys-F. W. Anderson and C. E. Tripp ABSTRACT: In plywood layup apparatus, veneer sheets are fed from a vertical stack onto a horizontal conveyor by a movable vacuum head that grips the uppermost veneer sheet in the stack and shifts it towards the conveyor. A pair of pinch rollers are positioned between the vacuum head and conveyor to separate a veneer sheet from the vacuum head by gripping and driving the veneer sheet forward onto the conveyor. Sometimes two veneer sheets, one superposed upon another, are fed between the pinch rollers by the vacuum head. This condition is detected automatically by sensing means which activate controls for lifting the upper pinch roller and holding the vacuum head in a sheet-feeding position. Friction force of the lower pinch roller acts on the lower veneer sheet only. The lower veneer sheet is driven forward onto the conveyor but the upper veneer sheet is held stationary by the vacuum head. After the lower veneer sheet has been separated and spaced from the upper veneer sheet, the upper pinch roller is lowered, forcing the upper veneer sheet into driving contact with the lower pinch roller. Thus, the upper veneer sheet is separated from the vacuum head and driven forward onto the conveyor.

PATENIEI] AUG! 719m SHEET 1 0F 7 INVENTORS RONALD J. BILLETT TERENCE H. WEST Ja/ 7A?TORNEYS PATENTEUAUBIHHH 3,599,968

SHEET 2 [IF 7 F'I E El TIE-31. 1- I we l 23 I 26 '54 L31 0 2.5

PATENIED mm 7 |97| SHEET 3 UF 7 PATENIEmucnm: I 3.599.968-

saw u (If VENEER-SHEET-FEEDING APPARATUS CROSS-REFERENCE TO RELATED APPLICATIONS This application contains subject matter similar to that disclosed in the copending application of Terence H. West, assigned to the common assignee of this application, filed herewith on the same date of Dec. 24, 1969, and given Ser. No. 887,877.

Related subject matter is also found in the copending application of Ronald J. Billett et al., US. Ser. No. 81 1,929, which has been assigned to the same assignee as this application. I

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to sheet feeding or delivering by separators and conveyors, and more particularly, to veneer sheet feeding and separating apparatus that delivers single veneer sheets in sequence.

2. Description of the Prior Art In the manufacture of plywood, layup apparatus is used to feed veneer sheets to an assembly station. There, different grades of veneer used for face, middle and back panels are put together in sandwich fashion with glued core strips interspersed between, forming plywood. Typical plywood layup apparatus is disclosed in the pending application of Ronald J.

. Billett et al., US. Ser. No. 81 1,929, which has been assigned to the common assignee of this application. Veneer sheets are fed from a vertical stack at each storage station by a movable vacuum head that grips the uppermost sheet in the stack and shifts it towards a conveyor. A pair of pinch rollers is positioned between the vacuum head and conveyor to grip the veneer sheet and drive it forward onto the conveyor, thereby separating it from the vacuum head.

Sometimes two veneer sheets, one superposed upon another, are lifted from a stack by a vacuum head and fed between the pinch rollers. This creates aproblem because if both sheets are conveyed to the assembly station, the extra sheet will have to be discarded by an operator. Feeding to the assembly station must be in sequence with the proper number of face, back and middle veneer panels delivered for assembly. While the previously mentioned Billett et al., patent application shows means for detecting and warning operators of doubles on the conveyor, the extra veneer sheet must be manually removed and discarded by an operator.

SUMMARY OF THE INVENTION Double veneer sheets are detected and separated automatically, in accordance with the present invention, enabling each conveyor to deliver veneer sheets to the assembly station in sequence for assembly. This increases the efficiency of the assembly operation and provides for increased production with lower manufacturing costs.

Sensing means detect when a plurality of veneer sheets, one superposed upon another, are fed between a pair of pinch rollers by the upward deflection of the upper pinch roller. Upon detection, controls are activated to lift the upper pinch roller out of contact with the uppermost veneer sheet. Thus, the uppermost veneer sheet is retained gripped by a movable vacuum head which feeds veneer sheets between the pinch rollers, while the lower veneer sheet is driven forward onto a conveyor by the rubbing contact force produced by the lower pinch roller. The veneer sheets are thereby separated by shearing action. After the lower veneer sheet has been separated and spaced from the upper veneer sheet, the upper pinch ,roller is lowered, forcing the upper veneer sheet into driving contact with the lower pinch roller, increasing the drag force on the sheet to the point where it is sheared off the vacuum head. Then the upper veneer sheet is driven forward onto the .conveyor and separated from the vacuum head.

I BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram showing feed drive elements for a plywood layup apparatus embodying the present invention.

FIG. 2 is a schematic diagram showing a main frame and location of limit switches for the plywood layup apparatus shown in FIG. 1.

FIG. 3 is an enlarged section taken on line 3-3 of FIG. 2.

FIG. 4 is an enlarged view taken in the direction of arrows 4-4 of FIG. 3.-

FIG. 5 is an enlarged section taken on the line 5-5 of FIG. 4.

FIG. 6 is a side view, partly in section, of a veneer storage station illustrating in solid line a carriage positioned to grip veneer sheets and in phantom line, the carriage positioned to feed veneer sheets between a pair of pinch rollers.

FIG. 7 is an enlarged sectional view of the pinch rollers shown in FIG. 6.

FIG. 8 is an operational view of the pinch rollers shown in FIG. 7, with the upper roller elevated out of contact with an upper veneer sheet.

FIG. '9 is an enlargedside view of mountings for the pinch rollers shown in FIG. 7.

FIG. 10 is a section taken on line 10-10 of FIG. 9.

FIG. 11 is a schematic diagram of typical pneumatic circuits for regulating a movable gate, a carriage and an upper pinch roller.

FIG. 12 is a schematic diagram of a hydraulic circuit for elevating a stack of veneer sheets at a storage station.

FIG. 13 is a schematic diagram of an electrical circuit for plywood layup apparatus embodying the present invention.

FIGS. 14-20 are schematic views illustrating sequential operations of the plywood layup apparatus DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 illustrate a typical plywood layup apparatus 14 that feeds veneer sheets from a plurality of storage stations to a plywood assembly station 15 located downstream from the layup apparatus. Back veneer sheets are stored in a vertical stack 16a, supported on an elevator or lift table 18 at a rear storage station. Middle veneer sheets are stored in a vertical stack 16b supported on a lift table 20 at a front storage station, while face veneer sheets are stored in a vertical stack 16c, supported on a lift table 19 at a middle storage station.

An upper conveyor 21 feeds back veneer sheets from stack 16a to an upper ready station conveyor 22, while an intermediate conveyor 23, positioned under the upper conveyor, feeds face veneer sheets from stack to the same upper ready station conveyor. Middle veneer sheets are fed from stack 16b at the front storage station directly onto the lower ready station conveyor 24. Back and face veneer sheets are released in pairs from the upper ready station conveyor to assembly station 15 and middle veneer sheets are released alternately from the lower ready station conveyor to the assembly station between pairs of back and face veneer sheets. Core strips, not shown, are supplied to the assembly station from another direction after passing through a gluing machine, also not shown.

As shown in FIG. 2, plywood assembly apparatus 14 includes a frame 25 that provides horizontal and vertical support for conveyors 21, 22, 23 and 24. This frame also supports a movable carriage 26 at each storage station above the respective lift table for feeding veneer sheets therefrom to a respective conveyor. At each storage station, an auxiliary conveyor 17, shown in FIG. 3, extends laterally outward from the frame at a height equal to the elevation of lift table 20 in its lowermost position. Rotatable rollers 17R of the auxiliary conveyor form a support surface that enables a stack of veneer sheets to be transferred thereon to the upper surface of a lowered lift table. The lift table upper surface is formed with rotatable rollers 19R that receive a stack of veneer sheets from the auxiliary conveyor. A standby stack of veneer sheets is stored on each auxiliary conveyor while the stack of veneer sheets on the lift table is being depleted. When the lift table stack has been exhausted, the lift table is immediately lowered and the standby stack is shifted onto the lift table. Then operations are resumed.

Lift tables 18, 19 and are of the type disclosed in U.S. Pat. No. 3,110,476 of W. A. Farris which issued Nov. 12, 1963. Each lift table is raised by a hydraulic actuator similar to actuator 120, shown in FIG. 12, that elevates lift table 19. This actuator includes a cylinder 121 with a piston 122 fitted therein and a piston rod 129 extending outward from the piston to elevate table 19. Pressure line 123 connects the cylinder interior at a location behind the piston to a sump SU. A hydraulic pump 1P is connected in the pressure line to pump fluid from the sump to the cylinder. A discharge line 128 is connected between the sump and the pressure line at a location between the pump and cylinder. Valve 124 is connected in the discharge line and has a movable spool 125 that is operated by a solenoid 2SOL An entrance port 126 and an exit port 127 are provided in the valve and between when the spool regulates flow.

Lift table 19 is elevated by actuation of a motor 3MTR which turns pump 1P, forcing fluid behind piston 122 to elevate piston rod 129. When valve spool 125 is in the position shown, it blocks flow from inlet port 126 to outlet port 127 and pressure is maintained behind the piston. To lower the lift table, solenoid 2SOL is energized moving valve spool 125 to the right, providing communication between inlet port 126 and outlet port 127 to discharge fluid to sump SU.

Looking now at FIG. 2, a limit switch 6 LS is located for engagement by the top sheets on the veneer stack at the middle storage station. This switch is operated when the stack is raised and is not released until the last sheet is taken from the stack. A limit switch 8 LS is also located for engagement with the top veneer sheet on the stack when the stack is elevated to the proper feeding height but disengages when the stack level drops too low for the vacuum head to grip the upper veneerv These switches are spaced apart to sense the level at either side of the stack. A limit switch 7 LS is operated by the lift table when in its lowermost position. Similar switches are located above and below the stacks at the front and rear storage stations.

At each storage station, a rail R1, as shown in FIG. 3, is mounted on one side of frame and a rail R2 is mounted on the opposite side of the frame. These rails form a track upon which carriage 26 travels. This carriage is formed by hollow duct 27 that extends transversely of the rails. One end of the duct is slidably connected to rail R2 by a bracket 28 and a beam 29 n )unted intermediately on the duct has an arm 30 at each end thereof that slidably rides on rail R1. A fan housing 31 containing a fan, not shown, in mounted on the end of the hollow duct extending outward from rail R1 and a motor 4MTR is mounted on the fan housing to drive the fan. A skirt J2 is mounted on the hollow duct surrounding a bottom opening located intermediately between the rails and when the fan motor is energized to drive the fan, air is evacuated from the hollow duct creating a vacuum at the bottom opening within the skirt.

Carriage 26 is advanced and retracted by a pneumatic actuator 33 having a cylinder 34 connected to frame 25 as shown in FIGS. 4 and 5. A piston 35, shown in FIG. 11, fits within the cylinder and is connected by a rod 36 and a link 37 to beam 29. Pneumatic line 38 and 39 are connected to opposite ends of the cylinder in order to introduce air pressure on either side of the piston. A control valve 40 has a movable spool 41 therein to control the flow of air from pressure line 42 to lines 38 and 39. This valve is controlled by a solenoid 4SOL and when deenergized, the movable spool is in the position shown. Line 39 is pressurized causing piston 35 to retract, while line 38 is vented to atmosphere through the valve discharge line 43 which contains a restriction 43R for adjusting retraction of the piston. When the solenoid is energized, the movable valve spool shifts to the right pressurizing line 38 and venting line 39 to atmosphere through a discharge line 44 which contains a regulating restriction 44R. Thus, pressure is introduced behind piston 35 causing it to advance or move forward.

During feeding operation, motor 4MTR drives the fan continuously so that there is always a vacuum pressure at the opening within skirt 32. Lift tables 18, 19 and 20 maintain veneer sheets in a position for the uppermost sheet to be gripped by suction force against the skirt. Carriage 26 is normally in the position shown in solid line in FIG. 6 but moves forward when solenoid 4SOL is energized to the position indicated in phantom line for feeding veneer sheets to a respective conveyor 21, 23 or 24. A funnel guide 46, shown in FIGS. 3, 6, 9 and 10, is positioned at the downstream side of each storage station and has converging panels forming top, bottom and sides to guide veneer sheets between a pair of nip or pinch rollers 47 and 48 which strip the veneer from the skirt.

With reference to FIG. 10, lower pinch roller 47 has a shaft portion 49 extending from one end and a shaft portion 49' extending from the opposite end thereof. These shaft portions are journaled in pillow blocks 50 and 50', respectively, which are bolted to a flange projecting horizontally from brackets 51 and 51. These brackets are welded opposite each other on a pair of horizontal channels forming frame 25. A sprocket 52 is mounted on shaFt portion 49' for driving the lower pinch roller by a drive that will later be described.

Upper pinch roller 48 has shaft portions 53 and 53 extending from opposite ends thereof and joumaled in respective pillow blocks 54 and 54, as shown in FIG. 10. Pillow block 54 is bolted to a support arm 55, as shown in FIG. 9. The support arm is pivotably connected at one end by a pin 56 to a bracket 57 bolted to a vertical member of frame 25. The support arm end opposite from pin 56 is coupled by a pin 58 to a clevis end 59 of a piston rod 60 extending from a pneumatic cylinder 61. The pneumatic cylinder is coupled with a clevis end 62 of a bolt 63 that fits through a hole in a plate 64 welded to a horizontal channel forming frame 25. The bolt is locked to the plate by an upper arm nut 65 and a lower nut 66. Pillow block 54' is bolted to a support arm 55 mounted to frame 25 in the same manner as described for support arm 55 so no further description is considered necessary.

A bracket 67 is bolted to the horizontal flange of bracket 51 and has a vertical leg to which limit switch 23LS is side mounted. This limit switch is operated by a straight plunger 68 which opens the switch when depressed and closes the switch when extended. An anchor plate 69 is welded to the upper surface of support arm 55 above the limit switch and a carriage bolt 70 having a round head that contacts plunger 68 is locked to the plate by nuts 71 and 72. Similarly, limit switch 24LS is side mounted to a bracket 67' bolted to bracket 51' and has a plunger 68' A carriage bolt 70 is fastened to an anchor plate 69 fixed to support arm 55' in a position to contact plunger 68.

Upper pinch roller 48 can be elevated from a lowered position indicated in FIGS. 7 to the position shown in FIG. 8 by operation of pneumatic cylinders 61 and 61. These cylinders are operated by a pneumatic circuit which is shown in FIG. 11. A compressor C supplies air through a line 73 to a control valve 74 having a movable spool 75 therein operated by a solenoid 16SOL. A line 76 connects the control valve with cylinders 61 and 61 above pistons 77 and 77', while a line 78 connects the control valve with the cylinders below the pistons. When the solenoid is deenergized, the movable spools is in the position shown and compressed air flows through the control valve and the line 76 to above the pistons in the cylinders. The pistons are thereby forced to the bottoms of the cylinders and air on the opposite sides of the pistons is discharged therefrom through line 78 returning to control valve 74. A discharge line 79 vents the control valve to atmosphere and contains a speed control restriction 80 for regulating the retracting rate of the pistons. When solenoid 16SOL is energized, the movable spool 75 moves upward allowing air to pass through the valve from line 73 to line 78 forcing pistons 77 and 77' upward to the top of cylinders 61 and 61'. Air above the pistons is restriction 82.

Conveyors 21, 22, 23 and 24 are formed by a series of rollers 85 (shown in FIG. 1) that are driven by contact with endless belts 86 trained about pairs of pulleys 87. The rollers on each conveyor are turned slightly to one side to guide veneer sheets against a against a sideplate for lateral alignment on the conveyor. Upper conveyor 21 is driven by a motor SMTR connected by chain 88 to a sprocket 89 that drives pulley 87 at the upstream end of the conveyor. A chain 90 is trained about sprockets 91 and 92 mounted on adjoining pulleys 87 to transfer drive from upstream belt 86 to downstream belt 86. Power is transmitted from sprocket 89 by a chain 93 to a sprocket 52 which turns the lower pinch roller 47. The upper pinch 48 roller is normally in contact with the lower pinch roller and turns therewith, but when a veneer sheet passes between the pinch rollers, the upper pinch roller will rotate with movement of the veneer sheet thereunder.

The drive for intermediate conveyor 23 and upper ready station conveyor 22 is similar to the drive previously described for upper conveyor 21. Therefore, like numbers have been used to identify like parts, with the exception that the motor is identified as 7MTR. Similarly, lower ready' station conveyor 24 has a motor 9MTR which drives a chain 88 that turns a sprocket 89 connected to a pulley 87 at the upstream end of .the conveyor. A chain 93 engaged by a sprocket 89 drives a sprocket 52 which turns the lower pinch roller 47. Power is transmitted by a chain 95 to a double idler sprocket 96 and from the double idler sprocket by a chain 97 to a sprocket 98 on the lower pinch roller 47 above the upper ready station conveyor.

' With reference to FIG. 1, upper conveyor 21 has a gate G-l located midway between upstream and downstream endless belts 86 and a gate G-2 located at the downstream end 'thereof. Intermediate conveyor 23 has a gate G-3 located at the downstream end thereof before the upstream end of upper ready station conveyor 22. A gate G-4 is located at the downstream end of upper ready station conveyor 22 and a gate G-S is located at the downstream end of lower ready station conveyor 24. Each gate extends between horizontal side members of frame 25 and is pivotably mounted to move between an upright position blocking sheet movement on a conveyor to a lowered position enabling veneer sheets to pass over the gate.

Gate G-3, shown in FIG. 11, is typical of each gate and pivots about an axis 99 in response to movement of an attached arm 100. The arm is connected to a piston rod 101 extending from a pneumatic actuator 102 secured to frame 25. The actuator has a cylinder 103 with a piston 104 slidably fitted therein and connected to the end of rod 101 opposite from arm 100. An air line 105 is connected to the cylinder behind the piston and an air line 106 is connected to the cylinder ahead of the piston. A valve 107 is coupled to air lines 105 and 106 for regulating the flow of air to the cylinder from compressor C through a line 108. A movable spool 109 slidably fitted within the valve is operated by a solenoid 7SOL. When the solenoid is deenergized, the movable spool is in the position shown and compressed air from line 108 passes through the valve into line 105 behind piston 104. Rod 101 is extended from the actuator to hold gate G-3 in the upright position shown for blocking veneer sheets. The cylinder in front of the piston is vented to atmosphere through line 106, valve 107 and a discharge line 110 which has a control restriction 111 therein. When solenoid 7SOL is energized, spool 109 moves to to the left of the position shown and air is directed from line 108 through the valve into line 106 and in front of the piston. As the piston is driven to the left, rod 101 retracts and gate G- 3 pivots. to a'horizontal position that enables veneer sheets to pass over the gate. Air behind the piston escapes through a line 105, valve 107 and a discharge line 112 which has a control restriction 113 therein to limit the rate of retraction of the piston.

A sheet sensor switch llLS, shown in FIG. 2, is located upstream on conveyor 21 from gate G-1 and is operated by a sheet of veneer positioned in front of the sensor switch 17LS is operated by a veneer sheet at gate G-2; sheet sensor switch 13LS is operated by a veneer sheet at gate G-3; sheet sensor switch 20LS is operated by a veneer sheet at gate G-4; and sheet sensor switch 41LS is operated by a veneer sheet at gate G-S.

Complete electrical control circuits for plywood layup apparatus of the type shown are disclosed in the previously men tioned patent application of Ronald J. Billett et al., US Ser. No. 81 1,929. The electrical circuit shown in FIG. 13 represents the controls for feeding veneer sheets from stack 160 at the middle storage station onto intermediate conveyor 23 and it will be understood that similar circuits are provided to control feeding at the front and rear storage stations. Upper conveyor 21, intermediate conveyor 23 and lower ready station conveyor 24, together with appurtenant equipment, each constitute a veneer-sheet-feeding apparatus so the description of one is sufficient to understand the invention.

Operation of the veneer-sheet-feeding apparatus will now be described in conjunction with the electrical circuit shown in FIG. 13 and the sequential operational views shown in FIGS. 14-20. When two veneer sheets, one superposed upon the other are fed between pinch rolls 47 and 48, as indicated in FIG. 14 at the upstream end of intermediate conveyor 23, upper pinch roller 48 will pivot upward and close normally open limit switches 23LS and 24LS. Relays 2CR, 18CR and 4TD are energized together with solenoid 16SOL.

Energization of relay 18CR closes normally open contacts 18CR-1, 18CR-2, 18CR-3 and 18CR-4. With the closing of contacts 18CR-1, solenoid 4SOL is maintained in an energized state to hold carriage 26 in a sheet-feeding position, as shown in FIG. 15, even if limit switch 13LS-1 should subsequently open. There is no immediate reaction to the closing of contacts 18CR-2 and 18CR-3 but air horn AH sounds when contacts 18CR-4 close. Energization of relay 2CR closes normally open contacts 2CR-l and opens normally closed contacts 2CR-2. Thus solenoid ZSOL is energized causing valve 124 to open and discharge fluid to sump SU, while motor 3MTR is stopped, and hydraulic actuator lowers stack due to the weight of veneer sheets thereon. Energization of relay 4TD causes no immediate reaction due to the time delay period. Energization of solenoid 16SOL operates control valve 74 to lift support arms 55 and 55 between which upper pinch roller 48 is mounted. Lifting the upper pinch roller causes the upper veneer sheet to be driven forward onto intermediate conveyor 23, as shown in FIG. 16.

After a time delay period, relay 4TD opens normally closed switch 4TD-1 and closes switch 4TD-2. Thus, valve 124 is reset to prevent the discharge of fluid to sump SU and motor 3MTR is started to elevate stack 160.

When the lower veneer sheet contacts sheet sensor switch 131.8, as shown in FIG. 17, switch 13LS-1 opens and switch 13LS-2 closes. Solenoid 4SOL holds carriage 26 in a sheetfeeding position because it remains energized through closed contacts 18CR-1. Relay SCR is energized by the closing of switch l3LS-2 and closes normally open contacts SCR-l. Since both contacts 5CR-1 and 18CR-3 are now closed, stepping switch 2SSW is energized cocking the switch.

When there is no veneer sheet behind gate 6-4, as shown in FIG. 17, sheet sensor switch 20LS will be closed and solenoid 7SOL energized operating valve 107 to lower gate 0-3, as shown in FIG. 18. The lower veneer sheet will pass over gate G-3 and onto upper ready station conveyor 22, as shown in FIG. 18. When the lower veneer sheet moves out of contact with sheet sensor switch 13LS, as shown in FIG. 18, switch 13LS-1 closed and switch 12LS-2 opens. Contact relay SCR is deenergized and opens contact SCR-l. Stepping switch 2SSW is deenergized and steps, opening contacts 2SSW-1, 2SSW-3 and 2SSW5 and closing contacts 2SSW-2 and 2SSW-4.

Opening contact ZSSW-l breaks the auxiliary circuit for energizing solenoid 4SOL but the solenoid remains energized gate. Similarly, sheet through switch l3LS-l and holds carriage 26 in a sheet-feeding position. Closing contact 2SSW-2 provides an auxiliary circuit through contact 18CR-2 to maintain relay 18CR in an energized condition, although limit switches 23LS and 24LS are still closed. Opening contact 2SSW-3 deenergizes solenoid 16SOL operating control valve 74 to lower the upper pinch roller. The upper pinch roller forces the upper veneer sheet into contact with the lower pinch roller, as shown in FIG. 19. Closing contact 2SSW-4 energizes a circuit containing pushbutton PB and stepping switch 2SSW. If one veneer sheet had to be discarded, pressing the pushbutton, would operate the stepping switch to return to a normal feeding sequence. Normally, it is not necessary to operate the pushbutton since the veneer sheets are both used. Opening contact 2SSW-5 shuts off air horn AH.

When the upper veneer sheet contacts sheet sensor switch 13LS, as shown in FIG. 19, switch 13LS-l opens and switch 13LS-2 closes. Opening of switch l3LS-1 deenergizes solenoid 450i. and allows carriage 26 to return to sheet-gripping position over stack 160, as shown in FIG. 20. Contact relay SCR is energized with the closing of switch 13LS-2 and closes contacts SCR-l, energizing stepping switch 2SSW which results in a cocking of the stepping switch. When the upper veneer sheet passes over gate G-3 and out of contact with sheet sensor switch 13LS, as shown in FIG. 20, switch 13LS-l closes and switch l3LS-2 opens. Solenoid 4SOL is energized causing the carriage 26 to feed another veneer sheet to the pinch rollers 47 and 48, while contact relay 5CR is deenergized, opening contact SCR-l and deenergizing stepping switch ZSSW. Upon deenergization, the stepping switch steps, closing contacts 2SSW-l, opening contacts 2SSW-2 which deenergize relay 18CR, closing contacts 2SSW-3 and 2SSW-5, and opening contacts 2SSW-4. Thus, the circuit is in normal operating condition to receive veneer sheets at the pinch rollers.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation can be made without departing from what is regarded to be the subject matter of the invention.

What we claim is:

l. Veneer-sheet-feeding apparatus comprising a power-driven conveyor;

means for gripping veneer sheets located adjacent one end of the conveyor;

means for shifting the gripping means to carry veneer sheets to the conveyor;

a pair of pinch rollers located between the gripping means and conveyor through which veneer sheets are fed for separation from the gripping means;

means for sensing a plurality of veneer sheets, one superposed upon another, located between the pinch rollers; and

means responsive to detection of a plurality of veneer sheets between the pinch rollers for spacing the pinch rollers to prevent separation of one veneer sheet from the gripping means while the other veneer sheet is driven forward on the conveyor.

2. The apparatus described in claim 1 wherein said pair of pinch rollers includes a power-driven lower roller and an idler upper roller; said idler upper roller being mounted to move out of contact with the uppermost veneer sheet when a plurality of veneer sheets are detected between the pinch rollers.

3. The apparatus described in claim 1 including means for holding the veneer-sheet-gripping means in a position to feed veneer sheets between the pinch rollers after a plurality of veneer sheets are detected until both sheets are separated therefrom.

4. The apparatus described in claim 2 including means for moving the idler upper roller into contact with the uppermost veneer sheet to separate the uppermost veneer sheet from the gripping means after the other veneer sheet has been segarated and spaced therefrom.

. The apparatus described in claim 1 including a pair of pivotal arms between which said idler upper roller is mounted and to which said sensing means is operatively connected for control by the simultaneous deflection of each pivotal arm.

6. The apparatus described in claim 3 including an actuator operatively connected to the pair of pivotal arms for elevating the arms and moving the idler upper roller out of contact with the uppermost veneer sheet when a plurality of veneer sheets are detected between the pinch rollers.

23 33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,599,968 Dated A s; 1,1, 1,911.

I RONALD J. BILLETT ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4 line 16 after "veneer" insert sheet Column 4 line 37 after "upper" delete arm Column 5, line 8 delete "against" (second occurrence) Column 6 line 68 change "closed" to closes Column 6, line 68 change "l2LS-2" to l3LS-2 Column 8 line 33 change "claim 1" to claim 2 Signed and sealed this 1 1 th day of July 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. Veneer-sheet-feeding apparatus comprising a power-driven conveyor; means for gripping veneer sheets located adjacent one end of the conveyor; means for shifting the gripping means to carry veneer sheets to the conveyor; a pair of pinch rollers located between the gripping means and conveyor through which veneer sheets are fed for separation from the gripping means; means for sensing a plurality of veneer sheets, one superposed upon another, located between the pinch rollers; and means responsive to detection of a plurality of veneer sheets between the pinch rollers for spacing the pinch rollers to prevent separation of one veneer sheet from the gripping means while the other veneer sheet is driven forward on the conveyor.
 2. The apparatus described in claim 1 wherein said pair of pinch rollers includes a power-driven lower roller and an idler upper roller; said idler upper roller being mounted to move out of contact with the uppermost veneer sheet when a plurality of veneer sheets are detected between the pinch rollers.
 3. The apparatus described in claim 1 including means for holding the veneer-sheet-gripping means in a position to feed veneer sheets between the pinch rollers after a plurality of veneer sheets are detected until both sheets are separated therefrom.
 4. The apparatus described in claim 2 including means for moving the idler upper roller into contact with the uppermost veneer sheet to separate the uppermost veneer sheet from the gripping means after the other veneer sheet has been separated and spaced therefrom.
 5. The apparatus described in claim 1 including a pair of pivotal arms between which said idler upper roller is mounted and to which said sensing means is operatively connected for control by the simultaneous deflection of each pivotal arm.
 6. The apparatus described in claim 3 including an actuator operatively connected to the pair of pivotal arms for elevating the arms and moving the idler upper roller out of contact with the uppermost veneer sheet when a plurality of veneer sheets are detected between the pinch rollers. 